Photoflash lamp with yttrium combustion filling

ABSTRACT

AN IMPROVED COMBUSTIBLE PHOTOFLASH LAMP IS DESCRIBED WHEREIN THE COMBUSTIBLE METAL FOIL IS YTTRIUM METAL. THE RISE TIME CHARACTERISTIC TO PEAK LIGHT OUTPUT IS SIGNIFICANTLY IMPROVED BY THE USE OF THE YTTRIUM COMBUSTIBLE METAL. THE ADDITION OF VARYING AMOUNTS OF YTTRIUM METAL TO   STANDARD COMBUSTIBLE METAL SUCH AS ZIRCONIUM ALSO IMPROVES THE RISE TIME TO PEAK LIGHT OUTPUT CHARACTERISTIC FOR THESE LAMPS.

June 27, 1972 K. F. ANDREW ETAL 3,672,814

PHOTOFLASH LAMP WITH YTIRIUM COMBUSTIBLE FILLING Filed Oct. 30, 1970 LEL 22 MILLISECONDS United States Patent Ofice 3,672,814 Patented June 27,1972 3,672,814 PHOTOFLASHLAMP WITH COMBUSTION FILLING Kenneth F. Andrew,East Pittsburgh, and Richard L. Tallman and Earl A. Gulbransen,Pittsburgh, Pa., assiguors to Westinghouse Electric Corporation,Pittsburgh, Pa.

Filed Oct. 30, 1970, Ser. No. 85,513

Int. Cl. F21lr 5/02 U.S. Cl. 431-95 6 Claims ABSTRACT OF THE DISCLOSUREAn improved combustible photoflash lamp is descirbed, wherein thecombustible metal foil is yttrium metal. The rise time characteristic topeak light output is significantly improved by the use of the yttriumcombustible metal. The addition of varying amounts of yttrium metal tostandard combustible metal such as zirconium also improves the rise timeto peak light output characteristic for these lamps.

BACKGROUND OF THE INVENTION One type of standard photoflash lamp in usefor the last several years is a zirconium shreaded foil combustible,super-pressure, oxygen-filled photofiash lamp. Such lamps havecontinuously been reduced in size while providing adequate light outputto make picture-taking very convenient.

The characteristic light output curve for photofia sh lamps to a certainextent determines their utility with various camera systems. Thezirconium shredded foil flash lamp exhibits a light outputcharacteristic curve which rises at a fairly rapid rate from theinitiation of light output to the peak light output in a period of about8 milliseconds, and then exhibits a gradual decay over approximately 30milliseconds. It is desirable for certain camera systems that a flashlamp be provided which has a light output characteristic curve whichexhibits as short a time for rise to peak light output as is possible.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is anelevational view in section of a photofiash lamp embodiment of thepresent invention.

FIG. 2 is a plot of the light output characteristic curves for both theyttrium lamp of the present invention, and for a standard zirconiumflash lamp. The relative light output is measured along the ordinate,and the time in milliseconds is plotted along the abscissa.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention can be betterdescribed by reference to the exemplary embodiment as shown in FIG. 1,and by the light output characteristic curves shown in FIG. 2. In FIG.1, photoflash lamp 10 comprises an hermetically sealed,light-transmissive glass envelope 12, ignition means which by way ofexample comprises an electrically conductive filament 18, for exampleformed of tungsten. A readily combustible conventional primer 20, suchas a several milligram mixture of powder zircohium and potassiumperchlorate is deposited on filament 18, or on the ends of lead-ins 14and 16, proximate filament 18. The electrically conductive lead-ins 14and 16 are sealed through the envelope 12 and electrically connected tothe ignition filament 18. A conventional blue lacquer coating 24 isgenerally disposed on the exterior envelope 12 to improve the colorcharacteristic of the light output and to prevent ruptureof the envelope12. The primary combustible material is a shredded metal 22 whichcomprises yttrium metal. For a photofiash lamp with a volume of about0.6 cubic centimeter, the shredded yttrium is preferably included in anamount of about 30 milligrams, which is about 5.7X10- gram-atom ofyttrium per cubic centimeter of lamp volume. The lamp is tipped-off andsealed containing an oxygen fill of about 8 atmospheres, although thiscan readily be varied from five to ten atmospheres, for example. Theyttrium combustible metal is preferably in the form of shredded foil,and as an example, the dimensions of the foil shreds are similar tothose of the conventional zirconium foil shreds. Measuremerits ofburning rates for yttrium foil of conventional foil dimension, i.e.about 1.8 square mils cross section, indicate that the yttrium burnsabout twice as fast as conventional zirconium foil.

The yttrium combustible content can be varied with a decrease in lightintensity as the amount is decreased and as a practical limit theyttrium content is at least about 3.7 -10- gram-atom per cubiccentimeter of lamp volume. The oxygen content can be widely varied, butis generally in the range of 70-100% stoichiometry with respect to theyttrium in forming yttrium oxide during combustion.

The typical light output characteristic curve for the lamp describedabove is shown in FIG. 2 as curve A. Relative light output is plottedalong the ordinate against the time in milliseconds. The first portionof curve A which runs along the zero axis is indicative of the time fromthe application of electrical potential to filament 18 until the primeris ignited and the combustible is burning to produce light output. Thistime is largely determined by the nature of the ignition system, i.e.for an electrical system such as described above it is about 3-4milliseconds. It is the portion of curve A which extends from theinitial production of light output at the end of this 3-4 millisecondsignition period, to the peak light output value, which is referred to asthe rise time to peak light output in this application. As is readilyseen in FIG. 2, the rise time to peak light output for the lamp of thepresent invention is about 4 milliseconds. The light output thengradually decays over approximately 30 milliseconds. Comparative datafor a zirconium flash lamp is shown by curve B of FIG. 2. The ignitiontime of about 3 to 4 milliseconds is about the same, but the time topeak light output from initiation of light output is about 8milliseconds, or about double the time which is observed for the lamp ofthe present invention.

It has also been discovered that yttrium metal can be added to zirconiummetal as the combustible to provide a flash lamp with an improved timepeak light output characteristic curve. For example, for the lamp sizedescribed above with a 20 milligram shredded foil filling which iszirconium and at least 20 atom percent yttrium the time to peak lightoutput from'initiation of light output is reduced to approximately 5milliseconds. The use of a hafnium metal combustible foil is disclosedin copending application S.N. 46,378 filed June 15, 1970, owned by theassignee of the present invention. The addit of e t 1. 2.,a m1i .tetr ttiymu ththsm i memaas mthe.an e s.smea s. s t afl si t gravid; hafniumcombustible results in an improvement of rise time over that attainedwith only hafnium so that the peak lightoutputhoccurs about 6milliseconds after initia; tion of light output. It is thus seen thatrelativelysmall amounts of yttriumin combination with otherconventionally used combustible metals results in an improved lightoutput characteristic.

The invention has been described with a conventional ignition system butis not limited thereto. A percussive ignition system can be utilized inigniting the improved combustible light-producing metal.

We claim as our invention: H p

1. A photoflash lamp combination comprising an hermetically sealedlight-transmissiveenvelope, ignition means within said envelope adaptedto be activated to initiate combustion, a combustion supportingatmosphere substantially comprising oxygen at a predetermined pressureenclosed by said envelope, wherein the improve: ment consists of animproved gombustible metal com: prising at least 4 atompercentfyttrium,whereby the rise time to peak light outputis shortfened,

2. The combination as specified in claim l, 'wherein said yttrium ispresent. in anamount of at [least about 55.7}{10 gram-atom cubiccentimeter of lamp vol- 7i) 1 0(l% stoichiometry with respect to theyttrium in forming yttrium. oxide durihg combustion. V

3. The combination as specified r in claim 2, wherein said yttrium ispreferably included in an amount of about 5.7 l0 gram-atomper cubiccentimeter-of lamp volume, and the oxygen press ure is about 8atmospheres.

4.'The combination as specified in claim 1-, :wherein i said combustiblemetal consists essentially ofryttrium;

5. Thecombinatiomas specified inclaim 1, wherein said combustible-metalsubstantially comprises zirconium l,

and the yttrium contentis at least about..20 atom percent of the totalcombustible metal.

6. The combination as specifiedin claim 1, wherein said combustiblemetal substantially comprises hafnium and the yttrium content is atleast about 4 atom percent of the total combustible metal.

v v References Cited UNITED STATES PATENTS EDWARD J. MICHAEL, PrimaryExaminer

